Incoming Gas cross bonded off cold water

[sparksburnout]

You've lost me here Midwest, what's 528 got to do with it?.

 

[Midwest]

You've lost me here Midwest, what's 528 got to do with it?.

Perhaps I misunderstood you. Just because the service is plastic, it doesn't mean you don't have to bond the internal metal pipes connecting to it.

 

[sparksburnout]

I completely agree mate. I would bond the internal copper even if it turned into plastic as it exited the building. However, I thought wire puller was getting at the suitability of the main gas bond to carry large fault currents, and presumably because he was stressing TNCS he meant if the neutral (and hence main earth) was lost the pipe route was not reliable, but if it's plastic outside it won't anyway will it?

 

[Midwest]

I completely agree mate. I would bond the internal copper even if it turned into plastic as it exited the building. However, I thought wire puller was getting at the suitability of the main gas bond to carry large fault currents, and presumably because he was stressing TNCS he meant if the neutral (and hence main earth) was lost the pipe route was not reliable, but if it's plastic outside it won't anyway will it?

Apologies, did misinterpret your post.

 

[sparksburnout]

Apologies, did misinterpret your post.

none required mate. Not sure if this is all worth getting worried about, as others have said. The pipe works all connected at the boiler anyway and any part of it in any installation could easily be disrupted by plumbing activity. How many people have ever seen or heard of a neutral being lost anyway??

 

[colshaws]

In my own house the CU and boiler are in one cupboard, the gas meter in a separate cupboard on opposite side of kitchen and incoming water at other end of the room. On my last Elecsa assessment I asked if i could bond from MET to the gas at boiler and onto water at boiler and confirm continuity to incoming water and gas and the assessor said put note on cert and all would be fine.

 

[sparksburnout]

In my own house the CU and boiler are in one cupboard, the gas meter in a separate cupboard on opposite side of kitchen and incoming water at other end of the room. On my last Elecsa assessment I asked if i could bond from MET to the gas at boiler and onto water at boiler and confirm continuity to incoming water and gas and the assessor said put note on cert and all would be fine.

seems logical to me

 

[Deleted member 26818]

A protective earth conductor may be a number of things, trunking, SWA armour or even pipe work (excepting any pipe work which contains a flammable material or one belonging to a utility company).

 

[Deleted member 9648]

I completely agree mate. I would bond the internal copper even if it turned into plastic as it exited the building. However, I thought wire puller was getting at the suitability of the main gas bond to carry large fault currents, and presumably because he was stressing TNCS he meant if the neutral (and hence main earth) was lost the pipe route was not reliable, but if it's plastic outside it won't anyway will it?

Nothing to do with fault currents,on a TNCS system the bonding conductors may carry a significant current under normal load conditions,thats why there is a requirement for 10mm.

 

[davesparks]

I don't have a regs book handy either....but I am certain this applies to supplementary bonding only, not main bonding.

It's protective conductors in general. You can also use cable armour/sheath, structural steel, conduit, trunking

 

[sparksburnout]

Nothing to do with fault currents,on a TNCS system the bonding conductors may carry a significant current under normal load conditions,thats why there is a requirement for 10mm.

come on then W/P, how under normal conditions can a TNCS system have "significant" current flowing through the EB?

 

[Deleted member 9648]

come on then W/P, how under normal conditions can a TNCS system have "significant" current flowing through the EB?

Because main bonding is connected to a metallic service at or near earth potential, and is electrically connected to the neutral terminal. Therefore a parallel path is created through which a proportion of the neutral current may divert. Do you think the required CSA of TNCS/PME bonding conductors are increased over TT/TNS for fun?

 

[davesparks]

come on then W/P, how under normal conditions can a TNCS system have "significant" current flowing through the EB?

Diverted neutral currents, which is the reason that PME supplies require larger main bonding and that the bonding size be maintained back to the PME terminal at the cutout.

 

[sparksburnout]

Because main bonding is connected to a metallic service at or near earth potential, and is electrically connected to the neutral terminal. Therefore a parallel path is created through which a proportion of the neutral current may divert. Do you think the required CSA of TNCS/PME bonding conductors are increased over TT/TNS for fun?

A proportion yes, but I don't think the word significant is particularly apt under normal conditions?

 

[davesparks]

A proportion yes, but I don't think the word significant is particularly apt under normal conditions?

Why not significant? If an old iron water main feeds a row of houses and each one has main bonding connecting that water main to the supply neutral then it will see a significant proportion of the neutral current

 

[Deleted member 9648]

A proportion yes, but I don't think the word significant is particularly apt under normal conditions?

Obviously no point in a 10mm bond then, do it in 6.0mm. No reason at all for the main bond on larger installations to be up to twice the CSA required on a TNS.

 

[Deleted member 26818]

Significant as in virtually all.
Problem with TN-S supplies, is that most are now PME, just not been upgraded to TN-C-S yet.

 

[sparksburnout]

I'm not questioning your knowledge w/p, just trying to get this straight. I understand how some current will flow through the EP, obviously it is a parallel path, but under normal conditions, on an average (let's say domestic) installation, it's not going to be large, certainly no where near that requiring 10mm? For example I just tried my own installation - with the shower and other stuff running I have a current draw of 41A through the tails, 40mA through the water bond and *****all through the gas, which is not surprising as it is plastic outside.(maybe come back to that just thinking about it). Am I, therefore, incorrect in thinking that the increased EP bond for TNCS systems is nothing to do with fault conditions including possible loss of neutral then?

 

[Deleted member 26818]

Due to the fact that the network neutral and earth are combined, any neutral current from the installation, will also be present in the earth conductors.
If incoming services are metallic and bonded, then diverted neutral currents from other installations that are bonded to the same services will also be present in the earth conductors.
A break in the Combined Neutral and Earth network conductor is another kettle of fish.

 

[sparksburnout]

Due to the fact that the network neutral and earth are combined, any neutral current from the installation, will also be present in the earth conductors.
If incoming services are metallic and bonded, then diverted neutral currents from other installations that are bonded to the same services will also be present in the earth conductors.
A break in the Cobined Neutral and Earth network conductor is another kettle of fish.

cheers Spin, I wasn't thinking of the bigger picture here. Methinks I might get me a copy of GN7

 

[Barrie Patrick]

I know what to do here. Install a bonding clamp on gas pipe with a short piece of 1mm connected to it. Tell kitchen fitter it is an aerial for your wireless bonding arrangement back to MET. He will definately believe you as he does not understand electrical type stuff thingys. Then tell customer it is free. Everyone will love you.

ROFLMAO :sorcerer: